1. Field of the Invention
The present invention relates to the control of soil erosion especially on the sides of rivers, drainage canals and riverbeds, on levees, beaches and the like. The present invention more particularly relates to an articulated erosion control system comprising a plurality of blocks, each of which is connected to the adjacent block by an interlocking connection provided by the blocks themselves which interlocking connection maintains horizontal block placement yet allows articulated movement in all directions of the blocks with respect to one another allowing conformation of the overall block system to the underlying terrain.
2. General Background
Erosion of land is a problem generally accompanied by water flow at the interface of the land and the water such as on the side of a riverbed or on a beach. Erosion can also occur as a result of rainfall as it proceeds through a particular basin to the river which empties that area.
Erosion is prevented in a natural sense by the growth of trees, grass, vegetation and the like with their root systems functioning to consolidate the underlying soil and prevent the mechanical erosion by both water and wind, but mainly water.
The natural vegetation is removed purposefully in many instances as when streams are channelized, or cleaned, or when levees are reformed. Other times vegetation removal and resulting erosion is natural, caused by flooding or the mechanical action of streams, rivers and generally by natural water flow.
Land which has been stripped of the natural vegetation is highly susceptible to erosion by wind and rain since the consolidation provided by vegetation is missing. This occurs on sloped terrain, as well as on terrain which is flattened.
The erosion problem is compounded by the removal of forrests, overgrazing of land, burning, construction of highways and the like, and the channelization of streams.
Planting rapidly growing vegetation on areas which have been stripped is sometimes successful but usually only where the vegetation grows rapidly and extensively enough so that the soil is protected. In areas where water is continually flowing such as on riverbanks, the growth of vegetation can usually not be done quickly enough to prevent erosion. Various systems of revetment have been used to augment or replace vegetation as an erosion barrier. The art has used loose fill barriers (riprap), continuous paving mats (some with weep holes to relieve pore pressure) and porous paving mats to control erosion.
"Riprap" which is known for control of erosion is basically a barrier or coverage comprising a plurality of large chunks of concrete (obtained, for example, in salvage operations) which are dumped in a particular area. The concrete chunks are usually of random size, with some so large as to not provide protection and washouts occur underneath. Further, the placement is often random, not adequately covering the subject area.
Solid continuous paving mats of concrete are highly costly because of the extensive amount of concrete required, the difficulty and costs of installation, and the problems of hydrostatic pore pressure which are created once the concrete is in place.
Paving blocks of concrete and other materials are known. Flexible porous concrete mats have been used as an erosion controlling protective surface.
Different patents directed to using revetment blocks and structures for preventing soil erosion have been issued. U.S. Pat. Nos. 242,689; 306,251; 314,022; 541,815; 572,762; 984,121; 994,999; 1,039,579; 1,162,499; 1,379,440; 1,597,114; 1,636,114; 1,691,848; 1,772,821; 1,822,602; 1,834,060; 1,847,852; 1,927,834; 1,939,417; 1,991,196; 1,993,217; 2,008,866; 2,047,197; 2,143,461; 2,159,685; 2,221,416; 2,295,422; 2,454,292; 2,577,170; 2,662,343; 2,674,856; 2,876,628; 3,096,621; 3,176,468; 3,210,944; 3,301,148; 3,343,468; 3,344,609; 3,386,252; 3,421,417; 3,597,928; and 4,227,829 disclose blocks and erosion control systems. The disclosures of the above U.S. patents are incorporated by reference herein.
U.S. Pat. No. 4,227,820 discloses a device comprising a matrix of cellular concrete blocks, each of which has internal passageways for cables to pass therethrough and interconnect a matrix of concrete blocks. The free ends of the cables are anchored into the ground after which operation the soil is spread over the blocks to reinforce surface thus controlling soil erosion.
U.S. Pat. No. 4,152,875 discloses a ground covering with adjoining plates which are clamped together by tensioning elements extending through the plates and parallel to them.
Nijdorn in U.S. Pat. No. 3,922,865 describes a mattress having a filter cloth with metal bars woven thereinto. Spaced concrete blocks are connected to these bars.
Appelton in U.S. Pat. No. 3,903,702 teaches the use of a revetment structure with similar interfitting units which form a flexible mattress. The units are provided with a series of interconnected ribs which make opposite sides of the units reflections of each other.
U.S. Pat. No. 3,597,928 discloses the use of porous flexible supporting sheets with mat of blocks which are placed on these sheets. Each mat consists of a plurality of blocks with drainage passageways therethrough and the blocks are secured to the sheets by adhesive means.
Nelson in U.S. Pat. No. 3,386,252 discloses a riprap structure for waterways, comprising rectangular blocks interconnected by a rod which extends through the blocks to provide for hooking the blocks at diagonally opposite corner ends and forming a matrix.
Dixon, U.S. Pat. No. 2,876,628 discloses a rapidly sinking articulated revetment for riverbanks comprising rigid blocks interconnected by flexible cables. The upper surface of each block has recesses from which openings extend through the whole block to provide for water passageways.
Louckes in U.S. Pat. No. 2,674,856 teaches the use of a similar flexible revetment mat which flexibility comes from the use of reinforced wires extending continuously from one concrete block to another to form a mattress for protection of river banks from erosion.
U.S. Pat. No. 2,159,685 describes a concrete riprap consisting of precast units connected by interlocking bars which pass through the orifices in the body of each unit.
A revetment in U.S. Pat. No. 2,008,866 comprises a number of rectangular concrete blocks arranged diagonally and hooked together by crossed rods to form a mat.
Mason in U.S. Pat. No. 1,987,150 teaches the use of a revetment containing filled asphalt in a certain proportion. A mat of such asphalt is placed adjacent a mattress consisting of slabs interlocked by cables or clips passed through the rings at each corner of a slab.
U.S. Pat. No. 1,359,475 describes a seawall construction comprising concrete panels with mating tongues and grooves at their edges and locked together by metal rods passing through the notches in the tongues and grooves.
Edinger in U.S. Pat. No. 1,164,708 discloses an embankment protection construction composed of interlocking rectangular concrete slabs with integrally made hook flanges and interengaging keys and sockets for locking the slabs in a mattress.
Edinger's U.S. Pat. No. 1,164,707 discloses a flexible concrete slab revetment construction composed of concrete slabs with integrally formed concrete joints interlocking the slabs, these slabs being preferably of a triangular contour.
U.S. Pat. No. 763,171 teaches the use of enbankment linings consisting of brick or stone blocks interlocked by wires passing through the perforations in the block bodies.
Villa in U.S. Pat. No. 554,354 discloses a covering for protecting banks from erosion, this covering comprising cement or terra-cotta prismatie plates interconnected by wires which pass through the plates to form rows of units adapted to cover riverbeds and banks, and free ends of wires are fastened to trees or piles driven into the bank.
Flexible mats, though generally more expensive than riprap or continuous paving barriers, are usually more stable. Flexible mats are not as prone to under-cutting erosion, by water, and provide greater relief for hydrostatic pressure. Flexible mats do exhibit failure, however, when individual elements of the mat are displaced by hydrostatic pressure or wave action, for example.
Applicant has provided an improved flexible mat structure which relieves hydrostatic pressure, conforms to the underlying surface, and retains its structural integrity. The noted advantages may be achieved at a cost which is competitive to known structures.